1. Field of the Invention
The present invention generally relates to an Inter-Carrier Interference (ICI) cancellation method based on Cyclic Prefix Reconstruction (CPR) and a receiver using the same in a Multiple-Input Multiple-Output (MIMO)-Orthogonal Frequency Division Multiplexing (OFDM) system. More particularly, the present invention relates to an Improved-Minimum Mean Square Error (I-MMSE) equalization method and an Improved-Capacity Mapping Ordering Scheme (I-CMOS) for reducing an ICI component during CPR, and a receiver using the same.
2. Description of the Related Art
A combination of OFDM and MIMO has attracted much interest as a technology for increasing the data rate of a frequency selective fading channel in a future-generation wireless communication system.
Since a MIMO system sends independent data streams through multiple Transmit (Tx) antennas by spatial division multiplexing, it has good capacity efficiency, compared to a Single-Input Single-Output (SISO) wireless system. Despite this advantage, the MIMO system suffers increased inter-channel interference as a capacity gain is increased.
OFDM is efficient in mitigating multipath distortion caused by the frequency selective channel. In OFDM, the frequency selective channel is converted to a set of flat fading channels for respective carriers. Hence, OFDM suppresses multipath distortion and enables high-speed transmission of a broadband signal.
The OFDM scheme adds a Cyclic Prefix (CP) before each OFDM symbol. The CP is set to be longer than a Channel Impulse Response (CIR) to thereby cancel Inter-Symbol Interference (ISI).
However, the spectral efficiency of an OFDM system decreases with the CP length. If the CP is not long enough, the ICI of a MIMO channel becomes too severe to be negligible, compared to that of a SISO channel.
Accordingly, there exists a need for a method for efficiently canceling ICI from a MIMO-OFDM channel, when a CP of an insufficient length is used.